The present invention relates to a novel and industrially-excellent process for producing a basic antibiotic.inorganic acid salt. For example, herein described is an industrially-excellent production process for producing an inorganic acid salt of an excellent antimicrobial agent having strong antimicrobial action on gram-positive bacteria and gram-negative bacteria, disclosed in JP-A 8-73462. More specifically, it relates to an industrially-excellent production process for producing, for example, (1R,5S,6S)-6-[(R)-1-hydroxyethyl]-1-methyl-2-{(2S,4S)-2-[(3R)-pyrrolidine-3-yl-(R)-hydroxy]methyl}pyrrolidine-4-ylthio]-1-carbapen-2-em-3-carboxylic acid.hydrochloride, a novel oxalate useful as a production intermediate, and a process for producing it.
In order to produce a basic antibiotic.inorganic acid salt, it is generally known to produce a free form, purify by column chromatography etc., and react the product with an inorganic acid.
For example, in the process disclosed in JP-A 8-73462, WO96/01261 or Example 9 of EP-A 773222 as a process for producing (1R,5S,6S)-6-[(R)-1-hydroxyethyl]-1-methyl-2-{(2S,4S)-2-[(3R)-pyrrolidine-3-yl-(R)-hydroxy]methyl}pyrrolidine-4-ylthio]-1-carbapen-2-em-3-carboxylic acid.hydrochloride etc., the objective product is obtained by subjecting a p-nitrobenzyl ester compound to catalytic reduction, purifying by reversed-phase silica gel chromatography, converting the product to a hydrochloride, and subjecting it to freeze-drying.
In the above-mentioned process in the prior art, the purification by chromatography is performed. Thus, a solvent is used in a large amount. Therefore, costs for the production rise to a considerable degree. Additionally, many problems as follows arise: difficulty in industrial processing in large amounts, the possibility of generating thermal cruelty (thermal decomposition) at the time of concentrating fractions, solvent remaining in the final product, disposal of waste liquid and environment pollution due to transpiration of the solvent. Thus, it cannot be said that the process is suitable for industry.
Moreover, it is necessary to perform subtle adjustment of pH when the free form is produced (neutralized) or converted to the hydrochloride. Thus, the process requires much labor and cost in industrial production. Moreover, freeze-drying is required in the last step, and results additional problems as follows: a further rise in the production costs, unsuitability thereof for processing in large amount and necessity of much
Thus, the present inventors made eager investigations to pursue a novel production process excellent in viewpoints such as production costs, operability (workability, safety and non-toxicity), the purity of final products, and the protection of the environment.
As a result, they have found out that the above-mentioned problems can be overcome at a stroke by using a novel oxalate (which will be in detail described below) as a production intermediate, and subjecting the oxalate to salt-exchange with an alkali earth metal salt an inorganic acid. Thus, they have accomplished the present invention.
Therefore, an object of the present invention is to provide a novel production process useful for producing a basic antibiotic.inorganic acid salt industrially, and a novel production intermediate useful for producing antimicrobial agents, and a process for producing it.
In one embodiment, the present invention is a process for producing a basic antibiotic.inorganic acid salt (I), which comprises subjecting a basic antibiotic.oxalate (II) to salt-exchange with an alkali earth metal salt (III) of an inorganic acid. 
wherein the ring A means the basic antibiotic; R10 means a protected functional group used in organic synthesis; Akxe2x80x94E means the alkali earth metal; and B means the inorganic acid.
In another embodiment, the present invention is a process for producing a basic antibiotic.inorganic acid salt (I), which comprises subjecting a basic antibiotic protector.oxalate (VI) to deprotection reaction; and then subjecting to salt-exchange with an alkali earth metal salt (III) of an inorganic acid. The present invention is also a process for producing a basic antibiotic.inorganic acid salt (I), which comprises subjecting a basic antibiotic protector.oxalate (VI) to deprotection reaction; then subjecting to salt-exchange with an alkali earth metal salt (III) of an inorganic acid; and then crystallizing the resultant or resulting compound by adding a poor solvent thereto.
The present invention is also a process for producing (1R,5S,6S)-6-[(R)-1-hydroxyethyl]-1-methyl-2-{(2S,4S)-2-[(3R)-pyrrolidine-3-yl-(R)-hydroxy]methyl}pyrrolidine-4-ylthio]-1-carbapen-2-em-3-carboxylic acid.hydrochloride (VIII) represented by the following formula: 
which comprises subjecting p-nitrobenzyl(1R,5S,6S)-6-[(R)-1-hydroxyethyl]-1-methyl-2-{(2S,4S)-2-[(3R)-pyrrolidine-3-yl-(R)-hydroxy]methyl}pyrrolidine-4-ylthio]-1-carbapen-2-em-3-carboxylate.oxalate (VII) represented by the following formula: 
(wherein PNB represents p-nitrobenzyl group) to deprotection reaction; then subjecting to salt-exchange with calcium chloride; and then crystallizing the resulting compound by adding methanol and/or isopropanol thereto.
The present invention is a process for producing a basic antibiotic.inorganic acid salt (I), in which the oxalate (II-I) of a carbapenem compound represented by the following formula is a basic antibiotic.oxalate (II), and which comprises subjecting the basic antibiotic.oxalate (II) to salt-exchange with an alkali earth metal salt (III) of an inorganic acid. 
The ring A represents a 3- to 7-membered ring having at least one nitrogen atom, and the ring A may be substituted with other than R6; R1 represents hydrogen or methyl group; R2 and R5 are the same as or different from each other and each represents hydrogen or a hydroxyl-protecting group; R3 represents a carboxyl-protecting group; R4 represents hydrogen, a lower alkyl group or an amino-protecting group; R6 represents (1) hydrogen, (2) an optionally protected hydroxyl group, carbamoyl, formimidoyl, acetoimidoyl or a lower alkyl group which may be substituted with a substituent represented by the formula: 
(wherein R7 and R8 are the same as or different from each other and each represents hydrogen, a lower alkyl group or an amino-protecting group) or (3) an amino-protecting group or an imino-protecting group; and m is 0 or 1.
The present invention is an oxalate (II-I) of a carbapenem compound represented by the following formula: 
wherein the ring A represents a 3- to 7-membered ring having at least one nitrogen atom, and the ring A may be substituted with other than R6; R1 represents hydrogen or methyl group; R2 and R5 are the same as or different from each other and each represents hydrogen or a hydroxyl-protecting group; R3 represents a carboxyl-protecting group; R4represents hydrogen, a lower alkyl group or an amino-protecting group; R6 represents (1) hydrogen, (2) an optionally protected hydroxyl group, carbamoyl, formimidoyl, acetoimidoyl or a lower alkyl group which may be substituted with a substituent represented by the formula: 
(wherein R7 and R8 are the same as or different from each other and each represents hydrogen, a lower alkyl group or an amino-protecting group) or (3) an amino-protecting group or an imino-protecting group; and m is 0 or 1.
Further, the present invention is a process for producing p-nitrobenzyl(1R,5S,6S)-6-[(R)-1-hydroxyethyl]-1-methyl-2-{(2S,4S)-2-[(3R)-pyrrolidine-3-yl-(R)-hydroxy]methyl}pyrrolidine-4-ylthio]-1-carbapen-2-em-3-carboxylate.oxalate (II-III), which comprises reacting p-nitrobenzyl(1R,5S,6S)-6-[(R)-1-hydroxyethyl]-1-methyl-1-carbapen-2-em-3-carboxylate-2-active compound (XIV) represented by the following formula: 
(wherein PNB has the same meaning as described above; and L means a leaving group) with (2S,4S)-2-{[(3R)-pyrrolidine-3-yl-(R)-hydroxy]methyl}-4-mercaptopyrrolidine.dihydrochloride (XV) represented by the following formula: 
and then converting the resultant into to an oxalate.
Herein, the basic antibiotic.inorganic acid salt (I) according to the present invention is an antibiotic having a basic salt in the molecule thereof, and is not limited so long as the antibiotic is combined with an inorganic acid to form a salt. Preferred examples thereof include the following:
(1) cefotiam (CAS Res.No.: 66309-69-1) hydrochloride;
(2) cefmenoxime (CAS Res.No.: 75738-58-8) hydrochloride;
(3) cefozopran(CAS Res.No.: 113981-44-5) hydrochloride;
(4) cefpirome(CAS Res.No.: 98753-19-6) sulfate;
(5) cefepime (CAS Res.No.: 123171-59-5) hydrochloride;
(6) cefoselis (CAS Res.No.: 122841-10-5) sulfate;
(7) cefotiam hexetil (CAS Res.No. 95789-30-3) hydrochloride;
(8) cefetamet pivoxil (CAS Res.No.: 65052-63-3) hydrochloride;
(9) cefcapene pivoxil (CAS Res.No.: 135889-00-8) hydrochloride;
(10) talampicillin (CAS Res.No.: 39878-70-1) hydrochloride;
(11) bacampicillin (CAS Res.No.: 37661-08-8) hydrochloride
(12) lenampicillin (CAS Res.No.: 80734-02-7) hydrochloride;
(13) pivmecillinam (CAS Res.No.: 32886-97-8) hydrochloride; and
(14) (1R,5S,6S)-6-[(R)-1-hydroxyethyl]-1-methyl-2-{(2S,4S)-2-[(3R)-pyrrolidine-3-yl-(R)-hydroxy]methyl}pyrrolidine-4-ylthio]-1-carbapen-2-em-3-carboxylic acid.hydrochloride (JP-A 8-73462, Example 9).
Next, the basic antibiotic.oxalate (II) according to the present invention is a starting material for producing the above-mentioned basic antibiotic.inorganic acid salt (I) by salt-exchange, and specific examples thereof include an oxalate of the above-mentioned basic antibiotic.
Next, the alkali earth metal salt (III) of the inorganic acid according to the present invention is not limited so long as it is an adduct salt made from the inorganic acid and an alkali earth metal such as beryllium, magnesium, calcium, strontium and barium. Preferred are alkali earth metal halide (IV) and alkali earth metal sulfides (V).
More specific examples of the alkali earth metal halides (IV) include beryllium fluoride, magnesium fluoride, calcium fluoride, strontium fluoride, barium fluoride, beryllium chloride, magnesium chloride, calcium chloride, strontium chloride, barium chloride, beryllium bromide, magnesium bromide, calcium bromide, strontium bromide, barium bromide, beryllium iodide, magnesium iodide, calcium iodide, strontium iodide, barium iodide etc.
Among these, magnesium chloride, calcium chloride, magnesium bromide, calcium bromide etc. are more preferred.
Examples of the alkali earth metal sulfates (V) include beryllium sulfate, magnesium sulfate and calcium sulfate.
The following will describe the process for producing the compound of the present invention in more detail. (See the following chemical reaction formula, wherein the ring A means a basic antibiotic; R10 means a protected functional group used in organic synthesis; Akxe2x80x94E means an alkali earth metal; and B means an inorganic acid.) 
(1) Step 1
The present step is a deprotection reaction in the case that a basic antibiotic.oxalate has a protected functional group in the molecule thereof.
The protected function group herein means a group obtained by protecting a functional group, such as a hydroxyl group, an amino group or a carboxyl group, and used in organic synthesis. The deprotection reaction can be conducted in an ordinary manner such as hydrolysis or reduction.
(2) Step 2
The present step is subjecting the basic antibiotic.oxalate (II) to salt-exchange with an alkali earth metal salt (III) of an inorganic acid, to give the target basic antibiotic.inorganic acid salt (I).
Herein, the amount of the alkali earth metal salt (III) of the inorganic acid used is not limited and is usually from 0.7 to 2.0 equivalents, preferably from 0.8 to 1.5 equivalent, and more preferably from 0.9 to 1.3 equivalent.
Herein, the solvent used is not limited. Specific examples thereof include water, lower alcohols, ketone solvents, ester solvents, ether solvents, formamide solvents and dimethylsulfoxide. These may be used alone or in the form of a mixture thereof. Among these, water and lower alcohols are preferred.
The manner of carrying out (operating) the salt-exchange is not limited. Usually, a solution wherein a necessary amount of the alkali earth metal salt (III) of the inorganic acid is dissolved is dropwise added to a solution of the basic antibiotic.oxalate (II).
Herein, a solvent wherein an alkali earth metal.oxalate which is by-produced by the salt-exchange is insoluble is selected at this time, the alkali earth metal.oxalate is precipitated and can easily be obtained by filtration. Therefore, this case is more suitable for industry.
The target basic antibiotic.inorganic acid salt (I) is in a solution state at this stage. Accordingly, extracting operation is necessary. However, by concentration of the solvent or addition of a poor solvent (solvent having low solubility), it can easily be precipitated as crystal.
In the case of concentrating the solvent, it may be completely dried. It is however allowable to concentrate it partially into a small-amount solution, cool the resultant solution or cause the resultant solution to stand still, thereby precipitating the target crystals.
In the case of using the poor solvent, the kind thereof is not limited. In general, methanol, n-propanol, isopropanol etc. are preferred.
In the present invention, the step 2 may be performed after the step 1 is performed to isolate and/or purify the basic antibiotic.oxalate (II). However, the steps 1 and 2 may be continuously performed by the so-called one-spot reaction.
In this case, the deprotection reaction solution can be used, as it is, for the salt-exchange. As a result, column chromatography, pH adjustment and freeze-drying become unnecessary. Therefore, this case is excellent in industrial operability, reduction in production costs, processing in large amount and environment protection.
(1R,5S,6S)-6-[(R)-1-hydroxyethyl]-1-methyl-2-{(2S,4S)-2-[(3R)-pyrrolidine-3-yl-(R)-hydroxy]methyl}pyrrolidine-4-ylthio]-1-carbapen-2-em-3-carboxylic.acidoxalate (II-IX) according to the present invention, which is represented by the following formula: 
is a novel compound and is useful for a production intermediate.
Herein, the oxalate (II-I) of the carbapenem compound according to the present invention is represented by the following formula. 
Wherein the ring A represents a 3- to 7-membered ring having at least one nitrogen atom, and the ring A may be substituted with other than R6; R1 represents hydrogen or methyl group; R2 and R5 are the same as or different from each other and each represents hydrogen or a hydroxyl-protecting group; R3 represents a carboxyl-protecting group; R4 represents hydrogen, a lower alkyl group or an amino-protecting group; R6 represents (1) hydrogen, (2) an optionally protected hydroxyl group, carbamoyl, formimidoyl, acetoimidoyl or a lower alkyl group which may be substituted with a substituent represented by the formula: 
(wherein R7 and R8 are the same as or different from each other and each represents hydrogen, a lower alkyl group or an amino-protecting group) or (3) an amino-protecting group or an imono-protecting group; and m is 0 or 1.
In the above-mentioned definition, the hydroxyl-protecting group, the carboxyl-protecting group, the lower alkyl group, the amino-protecting group, the optionally protected hydroxyl, the imino-protecting group etc. are not limited so long as they are groups which are usually used in organic synthesis. More specific examples thereof include the same groups as described in JP-A 8-73462.
The oxalate (II-I) of the carbapenem compound according to the present invention has an asymmetric carbon atom or a double bond in the molecule thereof, and is in the form of an optically active substance, a diastereomer, or a racemic body. In the present invention, it is not limited and may be any one. About geometrical isomers thereof, the same matter is true.
More specific examples of the oxalate (II-I) of the carbapenem compound according to the present invention include the following compounds, though it is not limited thereto.
(1) p-Nitrobenzyl 6-(1-hydroxyethyl)-1-methyl-2-{[2-(azetidin-3-yl)hydroxymethylpyrrolidine-4-yl]thio}-1-carbapen-2-em-3-carboxylate.oxalate;
(2) p-nitrobenzyl 6-(1-hydroxyethyl)-1-methyl-2-{[2-(pyrrolidine-3-yl)hydroxymethylpyrrolidine-4-yl]thio}-1-carbapen-2-em-3-carboxylate.oxalate;
(3) p-nitrobenzyl 6-(1-hydroxyethyl)-1-methyl-2-{[2-(piperidine-3-yl)hydroxymethylpyrrolidine-4-yl]thio}-1-carbapen-2-em-3-carboxylate.oxalate;
(4) p-nitrobenzyl 6-(1-hydroxyethyl)-1-methyl-2-{[2-(piperidine-4-yl)hydroxymethylpyrrolidine-4-yl]thio}-1-carbapen-2-em-3-carboxylate.oxalate; and
(5) p-nitrobenzyl 6-(1-hydroxyethyl)-1-methyl-2-{[2-(azepin-3-yl)hydroxymethylpyrrolidine-4-yl]thio}-1-carbapen-2-em-3-carboxylate.oxalate.
Next, 6-(1-hydroxyethyl)-1-methyl-2-{[2-(pyrrolidine-3-yl)hydroxymethylpyrrolidine-4-yl]thio}-1-carbapen-2-em-3-carboxylate.oxalate (II-II) according to the present invention is represented by the following formula: 
wherein R3 represents a carboxyl-protecting group.
Lastly, p-nitrobenzyl(1R,5S,6S)-6-[(R)-1-hydroxyethyl]-1-methyl-2-{(2S,4S)-2-[(3R)-pyrrolidine-3-yl-(R)-hydroxy]methyl}pyrrolidine-4-ylthio]-1-carbapen-2-em-3-carboxylate.oxalate (II-III) according to the present invention is represented by the following formula: 
wherein PNB represents p-nitrobenzyl group.
Sequentially, p-nitrobenzyl(1R,5S,6S)-6-[(R)-1-hydroxyethyl]-1-methyl-1-carbapen-2-em-3-carboxylate-2-active compound (XIV) which is a starting material for p-nitrobenzyl(1R,5S,6S)-6-[(R)-1-hydroxyethyl]-1-methyl-2-{(2S,4S)-2-[(3R)-pyrrolidine-3-yl-(R)-hydroxy]methyl}pyrrolidine-4-ylthio]-1-carbapen-2-em-3-carboxylate.oxalate (II-III) according to the present invention, is represented by the following formula: 
(wherein PNB has the same meaning as described above; L represents a leaving group which is usually used in organic synthesis, and specific examples thereof include trifluoroacethoxy, methanesulfonyloxy, trifluoromethanesulfonyloxy, p-toluenesulfonyloxy and diphenoxyphosphoryloxy), and can be produced by the process ([0069]-[0076]) described in JP-A 8-73462.
Furthermore, (2S,4S)-2-[[(3R)-pyrrolidine-3-yl-(R)-hydroxy]methyl]-4-mercaptopyrrolidine.dihydrochloride (XV), which is a reaction reagent, is represented by the following formula, and can be produced by the process described in Example 3 of JP-A 8-73462 etc. 
The following will describe the process for producing the compound of the present invention in more detail. (See the following chemical reaction formula, wherein PNB and L have the same meanings as described above.) 
(1) Step 1
The present step is a step of reacting p-nitrobenzyl(1R,5S,6S)-6-[(R)-1-hydroxyethyl]-1-methyl-1-carbapen-2-em-3-carboxylate-2-active compound (XIV) with (2S,4S)-2-[[(3R)-pyrrolidine-3-yl-(R)-hydroxy]methyl]-4-mercaptopyrrolidine.dihydrochloride (XV), to give a free compound or p-nitrobenzyl(1R,5S,6S)-6-[(R)-1-hydroxyethyl]-1-methyl-2-{(2S,4S)-2-[(3R)-pyrrolidine-3-yl-(R)-hydroxy]methyl}pyrrolidine-4-ylthio]-1-carbapen-2-em-3-carboxylate.
The present reaction is not limited so long as it is a thioether-synthesizing process which is usually conducted in organic synthesis. The process can easily be conducted in the presence of a base so as to give a high yield.
The kind of the base used herein is not limited. Specific examples thereof include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkali earth metal hydroxides such as barium hydroxide and calcium hydroxide; alkali metal carbonates such as sodium carbonate and potassium carbonate; alkali metal hydrogencarbonates such as sodium hydrogencarbonate and potassium hydrogencarbonate; inorganic bases such as alkali metal hydrides, for example, sodium hydride; primary to tertiary organic amines such as triethylamine, diethylamine, N,N-diisopropylamine and ethylamine; aromatic amines such as pyridine; and aniline derivatives such as N,N-dimethylaniline. Among these, N,N-diisopropylamine is more preferred.
(2) Step 2
The present step is a step of converting the free compound of p-nitrobenzyl(1R,5S,6S)-6-[(R)-1-hydroxyethyl]-1-methyl-2-{(2S,4S)-2-[(3R)-pyrrolidine-3-yl-(R)-hydroxy]methyl}pyrrolidine-4-ylthio]-1-carbapen-2-em-3-carboxylate into an oxalate thereof, to give the target p-nitrobenzyl(1R,5S,6S)-6-[(R)-1-hydroxyethyl]-1-methyl-2-{(2S,4S)-2-[(3R)-pyrrolidine-3-yl-(R)-hydroxy]methyl}pyrrolidine-4-ylthio]-1-carbapen-2-em-3-carboxylate.oxalate (II-III).
The present step can be conducted in a conventional way for conversion to oxalates. Usually, 0.7 to 2.0 equivalents of oxalic acid, preferably 0.8 to 1.5 equivalent of oxalic acid, and more preferably 0.9 to 1.2 equivalent of oxalic acid is dissolved into a solvent such as dimethylsulfoxide (DMSO), and then the resulting crystals were collected by filtration. Though the resulting crystals have sufficient purity by only air-drying, a higher-purity product can be obtained by solvent-washing, recrystallization etc.